Paging systems have undergone significant changes in the past twenty years. Early paging units were simple radio receivers that beeped upon receipt of a paging signal. A user wearing the paging unit would then take some predetermined action upon receipt of the paging signal, such as calling a telephone number. The user had no other choice in how to respond when he or she received the paging signal, because the paging signal did not contain any information concerning the nature of the appropriate action to be taken.
With advancements in paging technology, it became possible to send message data to a paging unit. This message data can comprise alphanumeric messages that inform the user who initiated the page or what action to take upon receipt of the paging signal. For example, a message may tell the user to call home, call the office, stop by the dry cleaners, etc. As computer technology advances, future paging units will be able to receive digitized voice messages, thereby acting as answering machines as well as having the capability to transmit data back to a central location--a so-called two-way paging system.
Most modem paging systems use a central computer system that is connected to a public switched telephone network, and a plurality of base stations disposed throughout a geographic area. When the central computer receives a telephone call indicating that a page signal should be transmitted, the central computer assembles a paging message that includes the address of the desired paging unit and the message data. The paging message is then forwarded to each base station where it is simultaneously transmitted, thereby blanketing the geographic area with the paging message. While simulcast paging systems work well to ensure reception of the paging message, they are inefficient because a) only one paging message can be transmitted at a time, and b) the paging message is being broadcast to a far greater area than necessary in order to assure that the message is received. As more users carry paging units, it is desirable that paging systems be developed that can transmit multiple paging messages at the same time.